/*
// Definition for a Node.
class Node {
    int val;
    Node next;
    Node random;

    public Node(int val) {
        this.val = val;
        this.next = null;
        this.random = null;
    }
}
*/
class Solution {
    public Node copyRandomList1(Node head) {
        Map<Node,Node> map = new HashMap<>();
        Node cur = head;
        while(cur != null){
            map.put(cur, new Node(cur.val));
            cur = cur.next;
        }
        cur = head;
        while(cur != null){
            map.get(cur).next = map.get(cur.next);
            map.get(cur).random = map.get(cur.random);
            cur = cur.next;
        }
        return map.get(head);
    }
     public Node copyRandomList2(Node head) {
        if (head == null) {
            return null;
        }
        Node cur = head;
        Node next = null;

        while (cur != null) {
            next = cur.next;
            cur.next = new Node(cur.val);
            cur.next.next = next;
            cur = next;
        }
        cur = head;
        Node curCopy = null;

        while (cur != null) {
            next = cur.next.next;
            curCopy = cur.next;
            curCopy.random = cur.random != null ? cur.random.next : null;
            cur = next;
        }
        Node res = head.next;
        cur = head;

        while (cur != null) {
            next = cur.next.next;
            curCopy = cur.next;
            cur.next = next;
            curCopy.next = next != null ? next.next : null;
            cur = next;
        }
        return res;
    }
}